Node in a communication system with switchable antenna functions

ABSTRACT

Systems and methods of a node in a wireless communication system with switchable antenna functions are provided. In one exemplary embodiment, a method by a controller for configuring a switching network may include configuring the switching network for a first mode of operation associated with multiple-input, multiple-output (MIMO) communications. Further, the method may include configuring the switching network for a second mode of operation associated with beamforming communications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/702,542, filed Dec. 6, 2012, which is the National Stage ofInternational App. No. PCT/EP2010/058243, filed Jun. 11, 2010, all ofwhich are entitled “NODE IN A COMMUNICATION SYSTEM WITH SWITCHABLEANTENNA FUNCTIONS,” and all of which are hereby incorporated byreference as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to a node in a wireless communicationsystem, the node comprising at least a first antenna function, a secondantenna function, a first radio chain and a second radio chain. At leastat the start of a first mode of operation, each antenna function isconnected to a corresponding radio chain.

The present invention also relates to a method in a wirelesscommunication system, the method comprising the step: at the start of afirst mode of operation, connecting antenna functions to correspondingradio chains, each antenna function being connected to a correspondingradio chain.

BACKGROUND

The use of mobile phones and wireless broadband devices has increasedrapidly during the last decade, and it is expected to grow even fasterduring coming years. To meet these demands, operators must increase thecapacity in their communication systems.

A well-known way of increasing the capacity in communication systems isto integrate more than one antenna and radio chain, both at the basestations and at the user terminals, and use so-called MIMO (MultipleInput Multiple Output).

Today, a user terminal such as a mobile phone is mostly used for voicecommunication, but a clear trend is that more and more people are usingtheir mobile phones for data applications, e.g. streaming movies andmusic, chat, and the Internet in other ways. One problem with mobilephones is that their battery capacity is relatively limited, and it istherefore needed to re-charge the mobile phone battery frequently. Inthe future when more radio chains will be integrated in the terminals,the power consumption will increase and the battery must be rechargedeven more frequently. There is therefore a need for reducing the powerconsumption to increase the time between charging. In addition thecarbon-dioxide “footprint” of the device will be smaller.

WO 2009/080110 describes a device that combines two antenna elementsusing a beam-forming network and thereby optimizing the antenna gain andpolarization to the environment. However, the number of antennas and thenumber of active radios are fixed.

A mobile phone, or another wireless broadband device constituting a userterminal, in a MIMO system may experience a rank-one channel or have noneed for high data rates. For example, in line-of-sight scenariosbetween a user terminal and a base station, the propagation channeloften only supports one stream, unless both ends of the link have dualpolarized antennas. In such cases, the user terminal cannot, or doesnot, need to utilize multiple streams.

A similar situation is present in other types of nodes such as basestations and repeater stations.

There is thus a need for a more efficient use of antennas and radiochains in a node.

SUMMARY

The object of the present invention is to obtain a more efficient use ofantennas and radio chains in a node.

Said object is achieved by means of a node in a wireless communicationsystem, the node comprising at least a first antenna function, a secondantenna function, a first radio chain and a second radio chain. At leastat the start of a first mode of operation, each antenna function isconnected to a corresponding radio chain. The node further comprises aswitching network and a beamforming network, which switching network, atleast at the start of a second mode of operation, is arranged todisconnect at least one antenna function from its corresponding radiochain and connect said at least one disconnected antenna function toanother of said corresponding radio chains via at least a part of thebeamforming network, such that at least two antenna functions areconnected to the same radio chain at least at the start of the secondmode of operation. The node is arranged to perform beamforming for saidat least two antenna functions by means of said beamforming network, theswitching network being arranged to switch between the first mode andthe second mode.

Said object is also achieved by means of a method in a wirelesscommunication system, the method comprising the steps:

at the start of a first mode of operation, connecting antenna functionsto corresponding radio chains, each antenna function being connected toa corresponding radio chain;

at the start of a second mode of operation, disconnecting at least oneantenna function from its corresponding radio chain;

connecting said at least one disconnected antenna function to another ofsaid corresponding radio chains via at least a part of a beamformingnetwork, such that at least two antenna functions at the second mode ofoperation are connected to the same radio chain; and

using said beamforming network to perform beamforming for said at leasttwo antenna functions.

According to an example, the number of radio chains and antennafunctions is equal, where, in the first mode of operation, only oneantenna function is connected to each radio chain.

According to another example, the beamforming network comprises at leastone phase shifter and/or at least one attenuator.

According to another example, the node further comprises a control unitwhich is arranged to control the switching network and the beamformingnetwork.

According to another example, those radio chains from which an antennafunction is disconnected, are turned off.

According to another example, the first mode of operation corresponds toMIMO, Multiple Input Multiple Output, communication.

Other examples are disclosed in the dependent claims.

The main advantage with the invention is that the energy consumption formobile phones and other types of nodes is reduced. At the same time, thepossibilities to exploit performance-enhancing technologies formulti-antennas are available.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described more in detail withreference to the appended drawings, where:

FIG. 1 schematically shows a first example of a node according to thepresent invention;

FIG. 2 shows a polar antenna radiation diagram showing the function ofthe present invention;

FIG. 3 schematically shows a second example of a node according to thepresent invention; and

FIG. 4 shows a flow chart of a method according to the presentinvention.

DETAILED DESCRIPTION

With reference to FIG. 1, showing a first example, there is a userterminal 1 in a wireless communication system, the user terminal 1comprising a first antenna function 2, a second antenna function 3, afirst radio chain 4 and a second radio chain 5.

According to the present invention, the user terminal 1 furthercomprises a switching network 6 and a beamforming network 7, where theswitching network 6 comprises a first switch 8. The user terminal alsocomprises a second switch 9 b. Each switch 8, 9 b may each be in any oftwo states, a first state or a second state. The first state isindicated by a dashed line and the second state is indicated by a solidline.

The beamforming network 7 comprises a first connection 7 a and a secondconnection 7 b, where the first connection 7 a is connected to theswitching network 6 and the second connection 7 b is connected to thesecond switch 9 b.

In its first state, the first switch 8 connects the first antennafunction 2 to the first radio chain 4, and in its second state, thefirst switch 8 connects the first antenna function 2 to the firstconnection 7 a of the beamforming network 7.

In its first state, the second switch 9 b disconnects the secondconnection 7 b of the beamforming network 7 from both the second antenna3 and the second radio chain 5, and in its second state, the secondswitch 9 b connects the second connection 7 b of the beamforming network7 to both the second antenna 3 and the second radio chain 5.

At a first mode of operation, each switch 8, 9 b is in its first statesuch that the first antenna function 2 is connected to the first radiochain 4 and disconnected from the beamforming network 7, and the secondantenna function 3 is connected to second radio chain 5. The secondconnection 7 b of the beamforming network 7 is disconnected from thesecond antenna 3 and the second radio chain 5.

At a second mode of operation, each switch 8, 9 b is in its second statesuch that the first antenna function 2 is connected to the firstconnection 7 a of the beamforming network 7 and disconnected from thefirst radio chain 4, and the second connection 7 b of the beamformingnetwork 7 is connected to the second antenna 3 and the second radiochain 5.

Thus, at the second mode of operation, the antenna functions 2, 3 areconnected to the same radio chain 5, and by means of the beamformingnetwork 7 the user terminal 1 is arranged to perform beamforming for theantenna functions 2, 3. The switching network 6 is arranged to switchbetween the first mode of operation and the second mode of operation.

In this example, the beamforming network 7 comprises a phase shifter 9,where a control unit 10 is arranged to control these via a first controlconnection 12. The control unit is further arranged to control theswitching network 6 and the second switch 9 b via a corresponding secondcontrol connection 11 and third control connection 13.

The control unit 10 is arranged to perform control in dependence of thechannel, where the control unit 10 is connected to the first radio chain4 and the second radio chain 5 via a corresponding fourth controlconnection 14 and fifth control connection 15.

According to one control alternative, the user terminal 1 is in thefirst mode of operation and transmits, or receives, reference signalsvia both antenna functions 2, 3 separately. Based on channel and rankestimation, or feedback, the control unit 10 can decide to switch offthe first radio chain 4, and connect both antenna functions 2, 3 to thesecond radio chain 5 in accordance with the second mode of operation.

In this alternative, the second mode of operation comprises:

connecting the antenna functions 2, 3 to the second radio chain 5, and

connecting the antenna functions 2, 3 to the first radio chain 4 and thesecond radio chain 5, respectively, transmitting or receiving referencesignals via both antenna functions 2, 3 separately in short time bursts.

The second mode of operation thus comprises switching back to the firstmode of operation for relatively short time periods in order to transmitor receive reference signals via both antenna functions 2, 3 separatelyin short time bursts.

Based on these reference signals, the control unit 10 can choose toswitch back to the first mode of operation.

According to another control alternative, the user has no need of highdata rates. Then the control unit 10 can choose to switch to the secondmode of operation until higher data rates are required.

According to yet another control alternative, a user wants to have lowpower consumption in the user terminal 1 and therefore manually decidesto always use the second mode of operation.

FIG. 2 exemplifies how the beamforming network can be used when the userterminal is working according to the second mode of operation, whichmeans that both antenna functions 2, 3 are connected to the second radiochain 5. The user terminal, represented by its radiation pattern 23, iscommunicating with a first base station 24 and receives an interferencesignal from a second base station 25. The phase shifter 9 is used tosteer the resulting radiation pattern 23 of the two antenna functionssuch that it faces the first base station 24 and faces away from thesecond base station 25, which will be discussed more in detail below.

In order to obtain the desired result, a number of phase settings of thephase shifter 9 are tested, which will result in different shapes of theradiation pattern 23. It is desirable to achieve a radiation patternthat has high gain towards the first base station 24, which the userterminal communicates with, and low gain towards the second base station25 that interferes with the user terminal. The performance of thecommunication link between the first base station 24 and the userterminal is improved significantly.

An alternative way to find the phase setting is to use numericaloptimization to maximize the SINR, e.g. a gradient search.

Other metrics such as rank indicator or CQI may be used to check thequality of the communication link.

The present invention can be implemented in any wireless device that hasmore than one antenna and more than one radio. For example, if there arefour antenna functions and four radio chains, all four antenna functionscould be connected to one radio chain while three radio chains areturned off and thus energy is saved. Another alternative is to connecttwo antenna functions to one radio chain and the two remaining antennafunctions to another radio while two radio chains are turned off to saveenergy.

This will be described more with reference to FIG. 3 showing a secondexample of a more general character. Here, a node such as a userterminal 1′ comprises a first antenna function 15, a second antennafunction 16, a third antenna function 17 and a fourth antenna function18. The node further comprises a switching network 6′ and a beamformingnetwork 7′ and also a first radio chain 19, a second radio chain 20, athird radio chain 21 and a fourth radio chain 22. The node 1′ alsocomprises a control unit as in the first example above, which is notshown for reasons of clarity. Here, the second switch of the firstexample should be understood to be implemented in the beamformingnetwork 7′, which of course will be constituted by three switches here.

Three different states are indicated, where the first state correspondsto the first mode of operation according to the first example above andthe second state and third state correspond to the second mode ofoperation according to the first example above

In a first state, as indicated with solid lines between the beamformingnetwork 7′ and the radio chains 19, 20, 21, 22, all the antennafunctions 15, 16, 17, 18 are connected to all the radio chains 19, 20,21, 22.

In a second state, as indicated with dashed lines between thebeamforming network 7′ and the radio chains 19, 20, 21, 22, the antennafunctions 15, 16, 17, 18 are connected to the second radio chain 20, thethird radio chain 21 and the fourth radio chain 22, the first radiochain 19 being disconnected and turned off.

In a third state, as indicated with dot-dashed lines between thebeamforming network 7′ and the radio chains 19, 20, 21, 22, the antennafunctions 15, 16, 17, 18 are connected to the third radio chain 21 andthe fourth radio chain 22, the first radio chain 19 and the second radiochain 20 being disconnected and turned off.

The control alternatives discussed above regarding control of theswitching network are of course applicable for the second example, aswell as for any configuration which uses the present invention.

Turning off a radio in a mobile phone 1 is equivalent to reducing theSINR on that antenna port in a MIMO (Multiple Input Multiple Output)system. Therefore, a mobile system utilizing MIMO communication regardsthis as if the number of possible streams is reduced and actsaccordingly. Therefore, the proposed concept implemented in a userterminal 1 does not require any changes in the mobile system.

With reference to FIG. 4, the present invention also refers to a methodin a wireless communication system, the method comprising the steps:

101: at least at the start of a first mode of operation, connectingantenna functions to corresponding radio chains, each antenna functionbeing connected to a corresponding radio chain,

102: at least at the start of a second mode of operation, disconnectingat least one antenna function from its corresponding radio chain;

103: connecting said at least one disconnected antenna function toanother of said corresponding radio chains via at least a part of abeamforming network, such that at least two antenna functions, at leastat the start of the second mode of operation, are connected to the sameradio chain; and

104: using said beamforming network to perform beamforming for said atleast two antenna functions.

The invention is not limited to the examples above, but may vary freelywithin the scope of the appended claims. For example, those radio chainsfrom which an antenna function is disconnected, may, or may not, beturned off.

It should be noted that although certain switch states are apparent at acertain mode of operation, these should generally be regarded to beapparent at least at the start of a certain mode of operation.

Preferably, the first mode of operation corresponds to MIMOcommunication.

An extension to using just one phase shifter is to use two phaseshifters and a hybrid combiner in a configuration as the “phase-to-powerconverter”. In this way, both the phase and amplitude of the two antennafunctions can be controlled by the means of two phase shifters.

The beamforming network 7, 7′ may have any suitable form and maycomprise any suitable components in dependence of the number of antennafunctions and radio chains. For example, the beamforming network 7 isshown comprising an attenuator 9 a.

The switching network 6 is described as only comprising one switch 8. Ofcourse the number and configuration of switches in the switching network6 may vary in dependence of the number of antenna functions and radiochains. The switches may be realized in any suitable technology,preferably semiconductor technology.

The examples above refer to a node or a user terminal, where a node isthe most general term. A node may refer to any type of user terminalsuch as a mobile phone or a laptop. A node may also refer to any type ofinstallation such as a base station or repeater station.

The second switch 9 b is used for isolating the second antenna function3 from the second connection 7 b of the beamforming network 7. Thisisolation may not be necessary, and may also be accomplished in othersuitable ways. The second switch or corresponding switches may, asindicated in the second example, be comprised in the beamforming network7′.

The switching network 6 and the beamforming network 7, 7′ may becomprised in one common unit.

The control alternatives discussed regarding how to control the switchstates are only examples of how such a control may be performed. Manyother types of control are of course conceivable.

The present invention relates to switching off one or more radios in anode, while maintaining the benefits of having access to all antennas.How the beamforming or combining of the antennas is performed is notwithin the scope of the present invention, although some examplesregarding how to find the desired phase settings are provided in thedescription. These should of course only be regarded as examples. Thereshould be at least two antenna functions and at least two radio chainsin the node.

The antenna functions may have any suitable form depending on thepresent application. In a mobile phone, an antenna function may beconstituted by a small meandered transmission line, and in a basestation it may comprise an array antenna.

What is claimed is:
 1. A method by a controller for configuring aswitching network, comprising: configuring the switching network for afirst mode of operation associated with multiple-input, multiple-output(MIMO) communications; and configuring the switching network for asecond mode of operation associated with beamforming communications. 2.The method of claim 1, wherein configuring the switching network for thefirst mode of operation includes sending, by the controller, to theswitching network, an indication to couple a first antenna to a firstradio chain and a second antenna to a second radio chain; and whereinconfiguring the switching network for the second mode of operationincludes sending, by the controller, to the switching network, anindication to couple the first antenna to the second radio chain so thatthe first and second antennas are coupled to the second radio chain toform at least a portion of a beamforming network used for thebeamforming communications.
 3. The method of claim 2, whereinconfiguring the switching network for the second mode of operationincludes sending, by the controller, an indication to disable the firstradio chain.
 4. The method of claim 2, wherein configuring the switchingnetwork for the second mode of operation includes sending, by thecontroller, to the switching network, an indication to decouple thefirst antenna from the first radio chain.
 5. The method of claim 2,wherein configuring the switching network for the first mode ofoperation includes sending, by the controller, an indication to enablethe first radio chain.
 6. The method of claim 1, wherein configuring theswitching network for the second mode of operation is responsive todetermining to configure the switching network for the second mode ofoperation based on at least one of a channel estimate and a channel rankestimate.
 7. The method of claim 1, wherein configuring the switchingnetwork for the second mode of operation is responsive to determining toconfigure the switching network for the second mode of operation basedon feedback from a base station.
 8. The method of claim 2, furthercomprising: during the second mode of operation of the switchingnetwork, sending, by the controller, to the switching network, anindication to couple the first antenna to the first radio chain so thatthe first radio chain is configured to receive a first reference signalusing the first antenna and the second radio chain is configured toreceive a second reference signal using the second antenna.
 9. Themethod of claim 8, further comprising: during the second mode ofoperation of the switching network and in response to at least one ofthe first radio chain receiving the first reference signal and thesecond radio chain receiving the second reference signal, sending, bythe controller, to the switching network, an indication to re-couple thefirst antenna to the second radio chain for the beamformingcommunications.
 10. The method of claim 8, further comprising: duringthe second mode of operation of the switching network and in response toan expiration of a predetermined time period, sending, by thecontroller, to the switching network, an indication to re-couple thefirst antenna to the second radio chain for the beamformingcommunications.
 11. A system for configuring a switching network,comprising: a controller operationally coupled to the switching network,wherein the controller is configured to: configure the switching networkin a first mode of operation associated with multiple-input,multiple-output (MIMO) communications; and configure the switchingnetwork in a second mode of operation associated with beamformingcommunications.
 12. The system of claim 11, wherein configuring theswitching network for the first mode of operation includes thecontroller being further configured to send, to the switching network,an indication to couple a first antenna to a first radio chain and asecond antenna to a second radio chain; and wherein configuring theswitching network for the second mode of operation includes thecontroller being further configured to send, to the switching network,an indication to couple the first antenna to the second radio chain sothat the first and second antennas are coupled to the second radio chainto form at least a portion of a beamforming network used for thebeamforming communications.
 13. The system of claim 12, whereinconfiguring the switching network for the second mode of operationincludes the controller being further configured to send an indicationto disable the first radio chain.
 14. The system of claim 12, whereinconfiguring the switching network for the second mode of operationincludes the controller being further configured to send, to theswitching network, an indication to decouple the first antenna from thefirst radio chain.
 15. The system of claim 12, wherein configuring theswitching network for the first mode of operation includes thecontroller being further configured to send an indication to enable thefirst radio chain.
 16. The system of claim 11, wherein configuring theswitching network for the second mode of operation is responsive to thecontroller being further configured to determine to configure theswitching network for the second mode of operation based on at least oneof a channel estimate and a channel rank estimate.
 17. The system ofclaim 11, wherein configuring the switching network for the second modeof operation is responsive to the controller being further configured todetermine to configure the switching network for the second mode ofoperation based on feedback from a base station.
 18. The system of claim12, wherein the controller is further configured to: during the secondmode of operation of the switching network, send, to the switchingnetwork, an indication to couple the first antenna to the first radiochain so that the first radio chain is configured to receive a firstreference signal using the first antenna and the second radio chain isconfigured to receive a second reference signal using the secondantenna.
 19. The system of claim 18, wherein the controller is furtherconfigured to: during the second mode of operation of the switchingnetwork and in response to at least one of the first radio chainreceiving the first reference signal and the second radio chainreceiving the second reference signal, send, to the switching network,an indication to re-couple the first antenna to the second radio chainfor the beamforming communications.
 20. The system of claim 18, whereinthe controller is further configured to: during the second mode ofoperation of the switching network and in response to an expiration of apredetermined time period, send, to the switching network, an indicationto re-couple the first antenna to the second radio chain for thebeamforming communications.